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Luteinizing hormone secretion as a response to a second naltrexone administration
L Yogev1, A Gottreich, Z T Homonnai
1Institute for the Study of Fertility, Serlin Maternity Hospital, Tel Aviv Medical Centre, Israel.
Summary
Naltrexone (Nalt) causes a temporary increase in luteinizing hormone (LH). A second Nalt dose shows a reduced effect due to a refractory period, with full LH response recovery after 8 hours.
Area of Science:
- Neuroendocrinology
- Reproductive Endocrinology
Background:
- Naltrexone (Nalt), an opioid antagonist, previously showed a rapid but transient increase in luteinizing hormone (LH) secretion.
- Subsequent Nalt challenges within 2 hours resulted in a blunted LH response, suggesting a refractory period.
Purpose of the Study:
- To determine the duration of the refractory period following naltrexone administration.
- To investigate the pituitary's responsiveness to LH-releasing hormone after naltrexone challenge.
- To explore the influence of diurnal variations on LH response to naltrexone.
Main Methods:
- Administered a second naltrexone injection at varying intervals (0, 2, 4, 8, 16, 24 hours) after the initial dose.
- Assessed LH secretion in response to naltrexone challenges.
- Verified pituitary responsiveness using LH-releasing hormone stimulation.
Main Results:
- Partial LH responsiveness to naltrexone was observed at 2 and 4 hours post-initial dose.
- Full LH secretory response to naltrexone was restored by 8 hours.
- Pituitary responsiveness to LH-releasing hormone remained intact, ruling out pituitary exhaustion.
- Diurnal variations in serum LH levels did not impact the naltrexone response.
Conclusions:
- A refractory period of at least 8 hours is required for a full LH response after naltrexone administration.
- Non-opioid systems may compensate for LH regulation during naltrexone blockade.
- The endogenous opioid system's re-emergence allows for renewed LH response to naltrexone once its levels decline.